Memory integrated circuit devices are well known. Memory cells can be read only (ROM), randomly accessible (RAM), static (SRAM), semi-static, dynamic (DRAM), programmable (PROM, EPROM, EEPROM), volatile, non-volatile (NVRAM) or of another memory type. The technology of transistor circuits used to form the memory cells can be varied as well. Exemplary types of technologies used include NMOS, PMOS, CMOS, bipolar, bi-CMOS or another circuit or technology type.
Typically, the memory cells are arranged in an array or matrix of memory cells and are accessed using column and row address decoders. The row address decoder typically generates a signal on a word line to select a desired row of memory cells. The column decoder then selects desired bit lines for certain memory cells in the row. Depending upon whether a write or read operation is desired, data is written into the selected memory cells or read out of the selected memory cells respectively. The organization of the array or matrix of memory cells can be varied. For a given capacity or total number of memory cells, they can be arranged so that N W-bit words can be accessed. For each address, a W-bit word is accessed providing W bits of data. Exemplary word widths, W, include 1 bit, 4 bits, 8 bits, 16 bits, 32 bits, and 64 bits. The number of words, N, then depends upon the desired capacity. Examples for the number of words include 1024 (1K) words; 4096 (4K) words, (1 meg) words. The total capacity of the memory in bits is then the product of the number of words and the number of bits per word (N×W).
Depending upon the organization of the memory, an address boundary of some type is usually associated with the memory. Typically, the upper bit or bits of the address establish an address boundary. For example, some memory devices are arranged or include circuitry to provide page mode addressing. Once a particular page has been accessed, accessing memory cells within the same page of addresses is typically faster. However if the page boundary is crossed by addressing a different page, the initial access within the new page is slower. An address boundary can be smaller than a page depending upon the memory type. The access time across a boundary is oftentimes an important performance consideration in memory selection.
The performance of memory integrated circuit devices, including power and speed, is often times very important in the selection of circuitry, organization and capacity. The performance of memory integrated into other types of integrated circuits can be an important consideration as well. Today some integrated circuits, including microprocessor integrated circuits, microcomputer integrated circuits, application specific integrated circuits, custom integrated circuits, digital signal processing integrated circuits, and application specific signal processing integrated circuits, commonly have large blocks of memory circuitry therein. Because memory has become much larger in these integrated circuits, the performance of memory has become very important.
Like reference numbers and designations in the drawings indicate like elements providing similar functionality. A letter after a reference designator number represents an instance of an element having the reference designator number.